Multiple switch-board for telephone-exchanges



(No Mudel.)

L. B. FIRMAN.

MULTIPLE SWITCH BOARD FOR TELEPHONE EXCHANGES. No. 252,576.

WVitnesses I11 vent 01 Patented Jan. 17,1882.

UNTTE S ATES ATENT Orrren.

LEROY B. FIRMAN, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE \VESTERN ELECTRICMANUFACTURING COMPANY, OF SAME PLACE.

MULTIPLE SWITCH=BOARD FOR TE.LEPHONE=EXCHANGES.

SPECIFICATION forming part of Letters Patent No. 252,576, dated January17, 1882.

Application filed January 7, 1881. (No model.)

To all whom it may conccrnl:

Be it known that I, Lnnor B. FIRMAN, of Chicago, Illinois, havediscovered certain new and useful Improvements in Multiple Switch-Boards for 'lelephone-Exchanges, of which the following is a full,clear, concise, and exact description, reference being bad to the accompanying drawings, forming a part of this specitication.

Prior to my invention the individual lines were grouped upon a singleswitch-board at the central office, or grouped upon two or more boards.In the latter case trunk lines were used when it was necessary toconnect a line of one board with a lineof another board. A largeexchange was thus divided up into a number of exchanges, which could beworked together, when occasion required, as one, by means of trunk linesbetween the boards.

When the number of subscribers increased, so that a single switchmancould not do the amountot'switchingrequired,Igavetheswitchman anassistant. I soon found, however, that a single switch-board would notaccommodate the number of attendants necessary to do the switching foran exchange of four or five hundred subscribers.

I find by the use of my new system of multiple switch-boards, ashereinafter described,

0 an exchangeofathousand or more subscribers may be successfullyhandled.

My invention consists in providing two or more switch-boards instead ofone. as heretofore,and so connecting the several lines there- 5 withthat any two lines can be connected on either of the boards, and alsoapparatus whereby attendants at a given board may without delay see whatlines are connected at other boards than their own.

My device is shown in the drawing, Figure 1, in which A A A representthe multiple boards, respectively. Each board must have as many terminalplates or switches I 2345, &c., as there are telephone-lines. Only fourtelephone-lines, a, 1;,0, and d, are shown. They are connected in any ofthe well-known ways at the subscribers stations, and are there providedwith any of the well-known outfits. When an extra wire is used forsignaling the central office the telephone-lines are grounded at theterminal stations and terminate at the central office in the insulatedterminal plates ofthe switch-boards. The indicator or dummyboard B isplaced in sight of all the attendant switchmen. I prefer to arrange themultipleboards in line and place the annunciator 0r dummy-boardcentrally in front of them, so that an attendant, by looking back, canseethe numbers upon the annunicator or dummy. There must be a number orother target corresponding to each subscribers terminal plate or switch.I have shown the figures 1 2 3 4 5 6 in the drawing, the first i'ourbeing indicated through the shields or targets at by dotted lines.

Suppose lines a and c are connected at multiple board A and lines I) andd at multiple board A as shown, by cord-s and plugs. The switchmen atthe boards, immediately on making these connections, notify theattendantat the dummy,who thereupon hangs up the shields or targets onover the figures l and 3 and 2 and I; and, in the same manner, when anyline is connected upon either of the multiple boards theligurewhichindicatesitsnumberis covered, and a switchman, by glancing at thedummy, sees what lines are connected. For example, if the subscriberconnected with plate 6 were to ask for the subscriber connected withplate 1, the attendant at board A, before making the connection, mustglance at the dummy-board, and in case he should see the target overfigure 1 he would know that the line wanted was in use at another board,and, instead of connecting plates 6 and I, he would notify thesubscriber connected with plate 6 that the person wanted is busy.

The central oifice may be notified when the subscribers are throughtalking by the American district system, or by sending a current to lineat either terminal station and tripping an annunciator number in thecircuit at the central office. As soon as the signal to disconnect isreceived the switchman pulls out the plugst'rom the terminal plates orswitches and immediately notifies the attendant at the dummy'board toremove the targets.

The dummy-board or indicator should be large enough to accommodatetargets or figures which may be readily distinguished by all theswitchmen. Figures maybe marked upon the shields o'r targets, and thusthe lines in use may be determined by observing the numbers indicated bythefigures upon the targets. Y

I do not limit my invention to any particular form of indicator,provided it is soplaced that the switchmen may readilyobserve whattelephone-lines are in use at other boards than their own.

The same number of the annunciator is disclosed when a giventelephone-line is con nected, whether the connection is made upon one oranother of the multiple boards.

There are matters of detail known to all acquainted with telephony thatmust be left to the judgmentot' the superintendent. Thus independentlines for signaling are especially convenient in large cities, yet someprefer to use the telephone lines for this purpose with a battery or amagneto-box. In the latter case the telephone-lines are grounded at thecentral oflice after passing respectively through a number ofannunciators and their respective switches or cut-outs on the differentboards.

Each station may be provided with a complete metallic circuit passingthrough an annunciator number and a switch on each board.

I do not limit my invention to any particular system of signaling thecentral otfice or running the circuits between the terminal stationsthrough the central oflice.

I disclaim the clearing-out annunciator in combination with the circuitof two connected lines, this being the subject-matter ofa claim inanother of my pending applications.

What I claim as my invention, and desire to secure by Letters Patent,is-

l. The combination of two or more switchboards at the central oliice ofa telephone-exchange system, to each of which the same telephone-linesare connected, whereby any two of these-lines may be connected togetherupon either of the multiple switch-boards.

2. Tire combination of two or more multiple boards to which the lines ofthe terminal stations are connected, and means, as described, wherebythe switchman may readily ascertain what lines are in use.

LEROY B. FI RMAN.

\Vi tnesscs:

G. W. EATON, Urns. A. BROWN.

